wood burning stoves
The moose likes Object Relational Mapping and the fly likes Update OneToMany relation Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Make it so: Java DB Connections & Transactions this week in the JDBC forum!
JavaRanch » Java Forums » Databases » Object Relational Mapping
Bookmark "Update OneToMany relation" Watch "Update OneToMany relation" New topic

Update OneToMany relation

Enrico Morelli
Ranch Hand

Joined: Jan 07, 2013
Posts: 30
Dear all,

I'm new to Java EE and I have a problem to add relation to an entity.
I've the following entities:



All works fine except when I try to relate a printer to an user. The first time the relation is written in the db. If I try to add another printer to the same user, I loose the first relation. I'm not able to add more than one printer to the same user. I tried a lot of solutions without result, the following is the last attempt to solve the problem.

Part of UsersEJB.java

Part of PrintersEJB.java

How can I solve the problem? Someone know book/sites where I can find real examples to use all the relations?

James Sutherland
Ranch Hand

Joined: Oct 01, 2007
Posts: 553
A few things,

Users and Printers make no sense as class names, they should be singular, User, Printer.

In your User the printer @OneToMany should use a mappedBy="owner" not a @JoinColumn.

Nowhere in your savePrinter code do you add the printer to the user, you need to do this.

TopLink : EclipseLink : Book:Java Persistence : Blog:Java Persistence Performance
Enrico Morelli
Ranch Hand

Joined: Jan 07, 2013
Posts: 30

in the mean time I find the solution (like you suggested) to add

I agree. Here's the link: http://aspose.com/file-tools
subject: Update OneToMany relation
jQuery in Action, 3rd edition